1. Field of the Invention
The present invention relates to a photopolymerizable composition and a recording material using the same. In particular, it relates to a photopolymerizable composition and a recording material which can be used favorably in various fields, having improvements in sensitivity, storability of unprocessed stock, surface yellowing (stain) resistance, and light fixation.
2. Description of the Related Art
A photopolymerizable composition basically contains a photopolymerization initiator and an addition-polymerizable compound containing two or more ethylenically unsaturated bonds in its molecule (also referred to hereinafter as “multifunctional monomer”), and is cured by irradiation with light thereby changing its adhesiveness or making it insoluble with solvent. Owing to these properties, the photopolymerizable composition is used widely in such areas as photography, printing, metallic surface processing, and in ink. Much literature is available describing functions and applications of photopolymerizable compositions (for example, J. Kosar: Light Sensitive Systems, J. Wiley & Sons, New York, 1965, pp. 158–193, and K. I. Jacobson, R. E. Jacobson: Imaging Systems, J. Wiley & Sons, New York, 1976, pp. 181–222)).
Image formation systems utilizing photosensitive microcapsules, in which a photopolymerizable composition is encapsulated in microcapsules, have been proposed recently as methods of image formation that use a photopolymerizable composition. For example, Japanese Patent Application Laid-Open (JP-A) Nos. 57-124343, 57-179836 and 57-197538 disclose a method of forming dye images involving a coloration sheet on which a photopolymerizable composition comprising a vinyl compound and a photopolymerization initiator and microcapsules containing a dye have been coated. The sheet is first exposed to light, then placed on an image-receiving sheet and the entirety thereof is pressed.
JP-A Nos. 03-4087827 and 04-211252 describe photosensitive heat-sensitive coloration recording materials containing two components. One of the two components is encapsulated in microcapsules, and the other is a curable compound in a photosetting composition, or, together with a photosetting composition, is contained outside of the microcapsules. As an example of the latter, a photosensitive heat-sensitive recording material is described which is provided with a layer containing microcapsules that encapsulate an electron-donating colorless dye and a photosetting composition outside of the microcapsules that contains an electro-receiving compound, a polymerizable vinyl monomer, and a photopolymerization initiator.
As described above, recording materials utilizing a photopolymerizable composition enable image recording in a completely dry system without using, for example, a developing solution. Their use is very preferable as waste harmful to the environment is not generated.
Regarding sensitization, use of inexpensive infrared laser and blue to red-range light would be advantageous to image recording on photosensitive recording materials, however, a majority of recording materials that make use of photosensitive compositions are sensitized with UV or short-wavelength visible light and not with visible to infrared-range light, or are poor in sensitivity even if they can be sensitized. As a result, formed images are not vivid, or may have poor contrast between image and non-image regions, and thus higher sensitivity is desirable.
A composition containing a thiol-containing compound as a polymerization assistant has thus been proposed by the inventors as a photopolymerizable composition usable in various recording materials, in response to the need for higher sensitivity and photosensitivity to light sources of wavelengths longer than those of visible rays (see, for example, JP-A No. 64-013144). A problem is, however, encountered with application of this photopolymerizable composition to recording materials. When, for examle, a vinyl sulfone-based hardener is used in a gelatin binder system, the polymerization assistant reacts with the hardener with results including deteriorated storage stability or photosensitivity that changes depending on humidity.
It has also been proposed that, an amine compound such as N,N-dialkyl aniline in Japanese Patent No. 2679830 or a benzylamine compound or the like in JP-A No. 2002-308922 be added as an oxygen quencher and thereby attain higher sensitivity, improve unprocessed stock storability and reduce surface stain. The effects, however, are still not sufficient and there is room for further improvements.
The present invention has been devised to solve the aforementioned problems in the related art, and to achieve the following objects.
An object of the invention is to provide a photopolymerizable composition which responds with high sensitivity not only to ultraviolet light but also to light in the visible to infrared renge and which is excellent in unprocessed stock storability.
Another object of the invention is to provide a recording material that is capable of highly sensitive recording using not only ultraviolet rays but also visible to infrared-range rays and that is excellent in various aspects including unprocessed stock storability, surface yellowing (stain) resistance, light fixation, and humidity dependence, all in a completely dry system not requiring use of, for example, a developing solution and without generation of any waste.